Various different forms of "open" front and rear sights have been used on hand guns and shoulder guns. A typical form of "open" front sight incorporates an upstanding blade member having vertical planar oppositely outwardly facing side faces or surfaces joined at their upper ends by a transverse horizontal top surface and a typical rear sight used in conjunction with such a front blade sight member includes a transfer body having a horizontal transverse upper surface and an upwardly opening notch formed therein opening upwardly centrally through the upper surface. A first form of typical rear sight includes a notch having vertical opposite side edges and a second form of typical rear sight includes a notch having upwardly divergent side surfaces. A line of sight is defined between the front and rear sights when the blade member is centered in the notch of the rear sight and the upper edge of the blade sight member is horizontally coextensive with the upper edge of the rear sight.
However, these previously known forms of conventional front and rear sight requires a person performing a sighting operation to ascertain and maintain equal spacing between the opposite sides of the blade sight member and the corresponding opposing sides of the notch. This must be accomplished while maintaining proper horizontal alignment between the upper surfaces of the front and rear sight and both lateral and vertical alignment of the target with the upper surface of the front sight. Accordingly, although an expert marksman may accomplish these alignment tasks almost automatically, even an experienced marksman has difficulty in accomplishing the various above alignment functions as well as the centering function of maintaining the forward blade sight centered in the notch of the rear sight.
In addition, the desired spacing between the sides of the notch of a conventional rear sight and the corresponding sides of an associated front blade sight member, in a sight picture, may vary according to the length of the arm of the user of an associated hand gun and the firing stance of the user of a long gun. Accordingly, a need exists for a notch defining rear sight to be adjustable to the extent that the width of the notch defined thereby may be varied.
Various different forms of sights including some of the general structural and operational features of the instant invention are disclosed in U.S. Pat. Nos. 821,821, 1,307,647, 2,335,881, 3,112,566, and 3,451,137 as well as German Pat. No. 665,662 and Great Britain Pat. No. 619,588.